This invention relates generally to bearing assemblies and, more particularly, to thrust bearing assemblies for mounting on a motor shaft.
In fractional horsepower electric motors, the rotor and motor shaft assembly tends to move axially within the housing and against the end plates and bearing means supported in the end plates. Such axial movement of the motor shaft must be limited for proper motor operation since excessive end play is detrimental to machine performance. Additionally, axial vibration gives rise to an objectionable knocking or bumping sound from within the motor. Consequently, thrust bearings are conventionally carried by the motor shaft between the rotor and the bearings mounted in the end plates.
Numerous configurations of such bearings are known. There are, for example, the configurations illustrated and described in U.S. Pat. Nos.: 3,573,510; 3,624,434; 4,955,791; 4,887,916; 3,553,511; 4,008,928; 3,789,251; 4,295,268; 4,245,870; 4,800,309; 4,308,478; and 4,711,590.
In the past, the thrust bearing arrangements for such motors have involved a number of separate components resulting in the need to assemble a number of loose parts at the time of motor assembly. Furthermore there was considerable tolerance build-up of the thrust assembly for free end play control of the motor rotor. Prior designs also tended to use elastomers, such as cushion washers, that deteriorated in the presence of lubricants and reactants that accumulate during motor operation over a wide range of temperature and other operating conditions.
According to the present invention, a thrust bearing assembly for mounting on a motor shaft includes a thrust plate and a thrust collar including first means for joining the thrust plate to the thrust collar, and second means for resiliently damping axial movement of the motor shaft. The second means is positioned between the thrust collar and the thrust plate.
Illustratively, the thrust collar comprises an outer perimeter, and the first means includes perimetrally spaced-apart resilient hook projections and a plurality of perimetrally spaced-apart torque transmitting projections.
In one embodiment of the invention, the thrust plate is formed to include perimetrally spaced-apart apertures to receive the resilient hook projections. The thrust plate further includes a plurality of perimetrally spaced-apart notches into which ends of the torque transmitting projections extend. The hook projections alternate with the torque transmitting projections on the thrust collar.
Further, the second means for damping axial movement comprises a wave spring. Also, the thrust collar is formed of a resinous material and is press fitted to the motor shaft so as to prevent rotational movement between the shaft and thrust bearing assembly, and to restrict lubricant flow along the shaft past the thrust bearing assembly.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.